The CEL on my 2004 Explorer 4.0L V6 SOHC came on and was missing. Hed auto parts store run check... said O2 sensor and cyl 1 and 2 were misfiring.. which I think it would b because the O2 sensors bad. So i changed the sensor, was running great... I disconnected the battery to reset the computer, hooked it back up and freaking thing goes into "limp mode". I checked all the fuses, did a rest on the fuel pump, on hooked the battery and the reconnected, no changes.... Anyone have an idea??? Remeber after I changed the sensor was runnign great until DX the battery????

 

The O2 code probably came on because of the miss fires on the cylinders... you cannot take the word of a non trained, misinformed parts jockey.....you realy need the services of a proper OBDII scanner with live data, instead of a code reader..

Time to pull all your sparks and check the condition of the engine (colour of tips).. Philip

 

Hopefully there is nothing wrong with the engine... it's only a year and half old. Thanks for the info

 

I was referring to condition of tune....cant have good burn to satisfy O2 if the plugs are not firing properly...... Philip